The present invention relates to surgically invasive apparatus for accessing a cataracted natural lens via the anterior chamber and a dilated iris, and for removing cataractous material from the lens.
Within the last ten years, there have been important advances in instrumentation and techniques for removal of cataractous-lens material. What has been termed phacoemulsification is perhaps the most important of these advances, and it should be noted that this term has applied to the use of ultrasonic energy, delivered at the small tip of a piezoelectric or magnetostrictive device; this is the currently favored means of locally fragmenting cataractous tissue, for extraction via a continuous flow of benign liquid. But use of such phacoemulsification devices calls for great skill, in that excessive delivery or misdirected delivery of ultrasonic energy can result in irreparable damage to the capsulary bag, the corneal endothelium, the retina and/or other parts of the eye.
It has also been proposed, but not generally accepted, to use local delivery of laser radiation to fragment cataractous material, to an extent permitting extraction in a continuous flow of irrigating liquid. But again, there is the prospect of irreversible damage to other parts of the eye, and great surgical skill is required.
Recent announcements have described another potential improvement in cataract surgery, attributed to Dr. J. M. Dodick, who uses the expression "laser phacolysis" in describing his procedure.* The Dodick procedure uses a 1,064-nm Nd:YAG laser to supply energy via an optical fiber. The energy is delivered within the probe tip of his instrument, for reflection by a titanium target that is inclined within the otherwise open end of the probe tip. Resulting shock waves are said to cause the nucleus and cortex to be lysed, and the debris is then aspirated out of the eye. FNT *"Use of Neodymium-YAG Laser for Removal of Cataracts is Reported", Ophthalmology Times, Dec. 15, 1989, pages 1, 6; "Nontarget Tissue of Rabbit Eyes Unharmed by Nd:YAG Phacolysis", Ophthalmology Times, Apr. 15, 1990, pages 1, 31; "Will Laser Become the Cataract Surgery Instrument of the '90s?", Ophthalmology Times, Aug. 1, 1990, page 40.
Throughout this case, the terms phacoemsulsification, phacolysis and tissue-fragmentation are deemed to be synonymous, in the sense that they apply to the use of externally supplied and locally delivered energy, whether ultrasonically applied or laser radiated, to break up and reduce cataractous material to a particular size small enough for external removal by the flow of an irrigating liquid.